A mobile device faces an ever accelerating race in higher integration of the mobile device in size and thickness along with higher demands in computation power and data transmission capabilities. In order to provide a seamless user experience, powerful hexa-core CPU systems along with GPU coprocessor were developed, for example, while multiplying the data send/receive capabilities by factors and reaching 300 MBit/s today with 1000 MBit/s on the near horizon. With Moore's law, helping to get more transistors build in less chip space, also device form factors shrink while adding further capabilities that contribute to component heating. At the same time, heat dissipation out of the system is reduced by the shrink and no active cooling, e.g. via a fan, may be possible due to design limitations.
Furthermore, leaps in technology nodes bring further challenges to tackle, especially by the so called leakage factor. Firstly, the generated leakage power increases exponentially with every technology generation. Secondly, the leakage rises exponentially with temperature. This leads to the fact that at high temperature, the leakage power may become the dominant factor for total power dissipation resulting in short battery life. Another drawback is the contribution of the additional leakage current to the heat generation which may lead to inconvenient device skin temperatures if not taken counteractions. In a worst case scenario, temperature regions may be reached, where a self-heating is triggered between the coupling characteristic of temperature and leakage. This may lead in an uncontrolled manner to a device overheating which may end in a software (SW) crash due to memory cell instabilities or even in damage of device hardware (HW).
Conventionally, thermal performance was provided using HW methods along with basic [i.e. single level] data throttling achieved. With transistor sizes going below 20 nm, the conventional cooling schemes are no longer acceptable. HW methods are based mainly on thermal heat spreading pads/materials to achieve a homogenous heat distribution and reducing thermal hot-spots. However, the cost per electronic device increases along with conflicts in new form factor design requirements.